Carbon is a versatile element because of its unique ability to form complexes in which the carbon atom has sp, sp2 and sp3 electronic configurations resulting in a wide range of structures and morphologies with widespread applications (Kang Z. C. and Wang Z. L, Mol. Catal. A: Chemical 118, 215-222). The search for new synthetic strategies for generating nanostructured carbon or carbon-hybrid materials is current in material chemistry, motivated by the natural abundance of carbon and therefore the cost effectiveness of carbon precursors and the promising applications of the resulting materials. Due to the intrinsic properties of the carbon materials, such as their high strength, high thermal resistance and light weight, carbon microspheres (CMS) can be used as high-strength composites, catalyst supports, lubricants and as wear-resistant materials (Jin Y. Z. et al 2005, Carbon 43, 1944-53).
High surface area mesoporous carbon materials (activated carbon) are important materials which are largely used in the industry for various applications e.g. pollution control treatment, water treatment and as a support in heterogeneous catalysts.
Different processes have been used to synthesize sphere like forms of carbon. N. J. Coville et al. have achieved the production of pure carbon spheres in the absence of a catalyst through the direct pyrolysis of hydrocarbon sources, acetylene and ethylene. Carbon microsphere-supported cobalt catalysts were synthesized and have shown good activity in the ethylene hydrogenation reactions (South African Journ. of Sci. 105, July/August 2009, 304-8).
Conventionally these carbon materials are synthesized by carbonization of various carbon sources such as coal, coconut hulls, acid sludges, petroleum coke and wood. These synthesized carbon materials have excellent physical properties such as high surface area and is inert in nature.
However, these high surface area materials when used in catalysis or as supports have very little influence on the reaction and the supporting active metal loaded on the carbon material leaches out resulting in deactivation of the catalyst and rendering it useless. This can be avoided either by protecting with hydroxyl groups or grafting various functional groups onto the surface of carbon which allows the introduction of additional functionality to tailor its surface and interfacial properties for the desired application. Due to the inert nature of carbon harsh reaction conditions are required for its functionalization. Frequently used carbon surface functionalization methodologies are aryl radicals coupling, amines, coupling of alkynes and azides at high temperatures. Recently carbon was functionalized by gas phase azide condensation method (J. Am. Chem. Soc., 2013, 135 (3), pp 1110-1116) which shows -the importance of functionalization of carbon microspheres. As these methods need high temperature and many expensive chemicals there is a need for alternative route for functionalization of carbons.
Maria-Magdalena Titirici et al, (Chem. Mater. 2009, 21, 484-490) provides a one-step aqueous route production of carbon microspheres loaded with carboxylic groups and hydroxyl groups using hydrothermal carbonization (HTC) of glucose in the presence of acrylic acid. The resulting carboxy groups on the surface of the carbon microspheres can be used for further functionalization aiming at different applications.
Furthermore, Shu-Hong Yu et al (Dalton Trans., 2008, 5414-5423) and Ying liang Liu, (J. Phys. Chem. C, 2009, 113 (19), 8455-59) disclose hydrothermal carbonization (HTC) process of biomass to produce functional carbonaceous materials.
Reference made to Chemistry Letters Vol. 38, No. 10 (2009) where glucose which is a 6-carbon sugar and Oxalic acid a strong organic acid has been used for synthesis of carbon microspheres. During synthesis of CMS under HTC carbonization it has to dehydrate and polymerization to form carbon spheres. Being used Oxalic acid it degrade and form water and end up with less surface hydroxyl groups. Being less functional onto surface of CMS the functionalization of other groups was not occurred. However in the present invention: Bagasse is used which mainly contains cellulose, pentosan, and lignin, which are polymers of large groups of carbons and upon HTC carbonation with Oxalic acid it does not dehydrate but only condensation and self assemble happen which leads to large number of hydrophilic functionalities —OH, —C═O, and COOH groups over carbon spheres and due to this very high available co-functional groups the grafting of other functional was possible.
However, there is still a need in the art to provide a process for grafting catalytically active functional groups on to the functionalized carbon microspheres and to derive a stable catalyst for various organic reactions.